The present invention relates to a touch panel controller operable to control a touch panel, and a semiconductor device having a touch panel controller, and a technique useful in application to a driver IC for e.g. display driving of a panel module with a touch panel incorporated in a liquid crystal display panel, and the touch detection control thereof.
For the purpose of increasing the accuracy of touch detection by a touch sensor, in the case of a mutual capacitance detection method, for example, the following are adequate to raise the frequency of a drive pulse for driving drive electrodes, and a sampling frequency of signal changes arising on detection electrodes as a result of this, and to increase the number of touch detections for each display frame. However, in case that the detection accuracy is kept high at all times, a large power will be consumed even with no touch.
Hence, by making faster the coordinate sampling cycle right after the start of touch when a flick operation can be performed and at the time when a drag operation is made faster, and setting a slow coordinate sampling cycle for other periods, the coordinate sampling can be performed at a minimum required speed. For instance, the coordinate sampling process is performed with a short (fast) coordinate sampling cycle t1 until a predetermined length of time has elapsed after the start of touch, whereas the sampling process is performed with a coordinate sampling cycle t2 which is longer (slower) than t1 after the predetermined length of time has elapsed. In case that the moving speed of a finger which touches the touch panel is increasing even after an elapse of the predetermined length of time, the sampling process is performed with the short coordinate sampling cycle t1 again.
The display control method like this is disclosed in e.g. Japanese Unexamined Patent Application Publication No. JP-A-2011-039709.